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| Cholesterol | Quick search: Lipids | Atherosclerosis | Diagnosis |
Lipids
LipoproteinsCholesterolDyslipidaemia ClassificationAtherosclerosisCV Risk FactorsClinical ManifestationLipids
Lipoproteins are macromolecular aggregates of lipids and apolipoproteins. Lipids can be divided into two main groups, simple and complex. The two most important simple lipids are cholesterol and fatty acids. Lipids become complex lipids when fatty acids undergo esterification to produce esters.1-3
Simple lipids: Cholesterol is a soft waxy substance present in all cells of the body. Most tissues can produce cholesterol, but it is synthesised primarily in the liver and small intestine. Approximately 50% of the cholesterol requirement is synthesised, whilst the rest is obtained from animal products in the diet. Cholesterol is important in the repair of cell membranes and in the synthesis of steroid hormones, vitamin D and bile acids. Fatty acids are the simplest form of lipid found in the body and are an important energy source. They exist as saturated, monounsaturated and polyunsaturated forms, distinguished by the number of bonds between the hydrocarbon chain and carbon atoms. The most common fatty acids in the body are stearic and palmitic (saturated), and oleic (monounsaturated). Fatty acids exist freely in the plasma mostly bound to albumin, but are stored in adipose tissue as triglycerides.1-3
Complex lipids: Triglycerides are mainly stored in adipose tissue and are the main lipid currency of the body. Phospholipids are glycerol esters containing two fatty acids. They have a water-soluble and a lipid-soluble surface and are an important component of the cell membrane. Cholesterol esters, oleate and linoleate, are the storage molecules of cholesterol in cells.1-3
Apolipoproteins: In order for these water-insoluble lipids to be transported around the body in the aqueous medium, blood, they are aggregated with apolipoproteins to form lipoproteins. These multimolecular packages consist of a hydrophobic core containing cholesteryl esters and triglyceride, surrounded by a hydrophilic surface layer of phospholipids, proteins and some free cholesterol. While structurally similar, lipoproteins vary in their proportions of component molecules and the type of proteins present.1-3
; "Structure of Lipoproteins")
References:
1. In: Fast Facts - Hyperlipidaemia. Eds Durrington P, Sniderman A. Health Press Ltd, Oxford, 2000. 1–17.
2. In: Manual of Lipid Disorders, 2nd Edition. Eds Gotto A, Pownall H. Williams & Wilkins, US, 1999. 2–10.
3. In: Statins - The HMG-CoA Reductase Inhibitors in Perspective. Eds Gaw A, Packard CJ, Shepherd J. Martin Dunitz 2000, 1–199.
 
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